In order for integrated circuit (IC) processing to be cost effective, the individual circuits, or chips, should be mass produced by using a semiconductor wafer to make many chips on a single substrate simultaneously. Typical processing for microelectronic mechanical systems (MEMS) involves extensive chip handling during processes such as the sacrificial layer removal and device testing. The ability to perform these processes in wafer form as opposed to chip form is very attractive. Carrying out the processing at the wafer level reduces the handling necessary because processing equipment must only move and align one wafer instead of many chips. Alignment, or registration, is very critical for die testing. After all wafer level processing has been done, the chips are separated and packaged. When the devices are separated from a wafer, wafer particles and dust, also known as dicing debris, is created. This dicing debris is then typically washed from the surface of the IC prior to bonding the chip to the package.
Micromechanical devices often have structures that are too fragile to survive exposure to some of the standard IC fabrication steps. An example is the digital micromirror device (DMD). DMDs are explained in U.S. Pat. No. 5,061,049 "Spatial Light Modulator and Method" which is assigned to Texas Instruments Incorporated. As described in the aforementioned patent, DMDs have a very small mirror suspended over an air gap above electrodes formed on the surface of a silicon substrate. Once this mirror is formed and the sacrificial material etched from the air gap, the DMD is very fragile. The devices cannot be exposed to liquids, for example during wafer cleanup steps, without destroying the mirror. Therefore, the devices must be cut and the dicing debris washed away before etching the sacrificial layer away from the mirror. This requires that the cleaning and etching steps, and any following steps, including testing be performed on the individual chips instead of a wafer.